For example, a solid oxide fuel cell (SOFC) employs an electrolyte of ion-conductive oxide such as stabilized zirconia. The electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (unit cell). The electrolyte electrode assembly is interposed between separators (bipolar plates). In use, predetermined numbers of the unit cells and the separators are stacked together to form a fuel cell stack.
Normally, as a fuel gas supplied to the fuel cell, a hydrogen gas produced from a hydrocarbon based raw fuel by a reformer is used. In the reformer, after a reforming raw material gas is obtained from the hydrocarbon based raw fuel such as a fossil fuel, e.g., methane or LNG, the reforming raw material gas is subjected to steam reforming or partial oxidation reforming, autothermal reforming or the like to produce a reformed gas (fuel gas).
For example, Japanese Laid-Open Patent Publication No. 2001-106507 discloses a reformer as shown in FIG. 13. The reformer includes a cylindrical container 1. Lid plates 2 are fixed to the opposite ends of the cylindrical container 1 in the axial direction. In the cylindrical container 1, a catalyst layer 3 filled with catalyst is supported by punching plates 4, 4a. In the catalyst layer 3, baffle plates 6 and 7 are provided alternately. The baffle plate 6 has an opening at a lower position, and the baffle plate 7 has an opening at an upper position. Cushion material 8 is provided above the catalyst layer 3.
In the catalyst layer 3, a gas flows through the openings of the baffle plates 6, 7 vertically in a zigzag pattern. According to the disclosure, in the structure, it is possible to prevent formation of short paths for the gas flowing in the catalyst layer 3.
In the conventional technique, normally, a large number of pieces of catalyst in the form of particles are filled in the catalyst layer 3 to ensure that the surface area of contact between the catalyst particles and the gas is large. However, the catalyst particles move easily in the catalyst layer 3 when the gas pressure or the like is applied to the catalyst layer 3. Under the circumstances, short paths may be formed in the catalyst layer 3 undesirably. As a result, in the catalyst layer 3, the desired surface area of the catalyst particles that contact the gas cannot be maintained. Accordingly, the reforming efficiency is lowered.